Conventional devices including as a part thereof a liquid tank having an outlet at a lower portion thereof include ink jet devices, such as the one disclosed in detail in the specification of U.S. Pat. No. 4,183,030, Jan. 8, 1980. The disclosed device comprises an ink tank having at its bottom a nozzle made of a thin metal pipe for guiding ink from the interior of the tank to the outside. By virtue of the hydrostatic pressure of the ink and a bias voltage impressed across the nozzle and an opposed electrode, the ink is held in a ready state, forming a meniscus at the nozzle tip. When a switching voltage is applied across the nozzle and the electrode, the ink is forced out from the nozzle in the form of a jet.
With this device, a reduction in the amount of ink in the tank causes a variation in the hydrostatic pressure at the nozzle, directly effecting the outflow of ink, such that when the ink jet device is used as a recording head, the amount of jetted ink is reduced to a degree which produces variations in the density of the recorded characters, in the size or width of drawn lines or in the ink atomizing frequency, consequently resulting in various defects such as deformed recorded characters, illegible characters, delayed responsiveness of the ink jet and recorded characters of impaired quality.
Accordingly in order to reduce the variations of hydrostatic pressure to the greatest possible extent, it has been attempted, for example, to use a tank having an increased bottom area and a reduced height. However, serious problems are still encountered when using such a device. For instance, if the ink jet device is used as the recording head of an X-Y plotter, there is a limitation on the increase in the size of the bottom area. Accordingly, in this case in which a capacity of the tank can not be increased, it may render one recording head unusable for a prolonged period of continuous time.